Editor's note: An earlier version of this story incorrectly stated that two children were among the four dead. Two children were wounded, but are being treated for their injuries.

The mother of the gunman who killed at least four people and wounded at least 10 others, including two children, in Northern California on Tuesday shared some information that could explain her son's state of mind before the shooting spree.

In a phone interview with the Associated Press, the woman, who identified herself only as Anne, revealed that her son had been feeling frustrated by an ongoing feud with his neighbors.

Two women embrace outside Rancho Tehama Elementary School, where a gunman opened fire Tuesday, Nov. 14, 2017, in Corning, Calif.  (AP Photo/Rich Pedroncelli)

"I'm on a cliff and there's nowhere to go," he reportedly told his mother about the situation.

A day before opening fire Tuesday at multiple “random” locations near Rancho Tehama Elementary School, the shooter called his mother and said "it's all over now," the AP reported.

The school is located in Rancho Tehama Reserve, an unincorporated area in Tehama County, about 100 miles north of Sacramento.

Anne also said she posted bail for her son in January after he was charged with stabbing one of the neighbors.

Although police have declined to identify the shooter, they confirmed the same man was charged in the January assault.

A woman and a child sit by an elementary school where a gunman opened fire in the community of Rancho Tehama Reserve in Corning, Calif., Tuesday, Nov. 14, 2017.  (AP Photo/Rich Pedroncelli)

Anne told the AP she was unaware of her son being involved in Tuesday's shooting until an AP reporter contacted her.

The shooter tried to access rooms at an elementary school to shoot more kids as part of a "bizarre and murderous rampage," police said at a news conference Tuesday night.

The shooter was killed by police after he opened fire.

Tehama County Assistant Sheriff Phil Johnston said that one of the victims was a woman who had been stabbed in the January attack.

School officials heard shots being fired about a quarter-mile away and the school went into lockdown mode, Johnston said. He added the incident "could have been much worse if it wasn't for the quick thinking" of the school's staff, who put the school in immediate lockdown mode without instruction from police. 

Johnston noted it was "monumental" that school workers took action when they did, because he believes they saved the lives of countless children.

The assistant sheriff said the gunman rammed his vehicle into a school fence, then walked onto school grounds with a semi-automatic rifle while wearing a protective vest.

After being unable to access classrooms due to the lockdown, it's believed the gunman became "frustrated" and went back to his car, and began shooting at people while driving, according to police.

"This guy was bent on driving by residences and arbitrarily shooting at them," Johnston said of the gunman. "This guy was on a killing rampage, he was driving up and down the street shooting at passerbys [sic], and uninvolved residences."

Crime tape blocks off Rancho Tehama Road leading into the Rancho Tehama subdivision south of Red Bluff, Calif., following a fatal shooting on Tuesday, Nov. 14, 2017.  (Jim Schultz/The Record Searchlight via AP)

A mother, who said she didn't know the gunman but was just driving past him with her three children, was shot. One of the children suffered a non-life-threatening injury, according to police. However, it was unclear if she was the victim of a gunshot wound or hit with shrapnel from a bullet-riddled car door.

“This is an individual that armed himself, I think, with the motive of getting even with his neighbors, and when it went that far, he just went on a rampage," Johnston added of the shooter, noting that authorities didn't suspect any connection to terrorism.

Investigators recovered a semi-automatic riflle, in addition to two handguns. Johnston said there was another weapon in the suspect's crashed vehicle that authorities had not yet recovered.

The officer noted there was a restraining order against the shooter, which he said would've limited his ability to possess firearms for a period of time, depending on the reason for the order.

More than 100 police officers were investigating seven different shooting scenes in the area. 

Brian Flint told the Record Searchlight newspaper after the shooting that his neighbor was the gunman.

"The crazy thing is that the neighbor has been shooting a lot of bullets lately, hundreds of rounds, large magazines," Flint said. "We made it aware that this guy is crazy and he's been threatening us." He added the suspect stole his truck.

Witnesses at the school described multiple rounds being fired. Coy Ferreira told KRCR he was dropping off his daughter at the school just before 8 a.m. when he heard a firecracker-like sound. The school’s secretary then ran out and told children to go inside because there was an active shooter. Ferreira said he ended up in a classroom with 14 students and witnessed a boy being struck by bullets.

The Tehama County Sheriff's Office has asked the Department of Justice to investigate the shooting, Johnston told KRCR. He added the FBI volunteered to investigate, as well.

California Gov. Jerry Brown said in a statement that he and his wife were "saddened to hear about today's violence in Tehama County, which shockingly involved schoolchildren. We offer our condolences to the families who lost loved ones and unite with all Californians in grief."

Vice President Mike Pence tweeted his condolences for the lives lost in the shooting, and said "We commend the effort of courageous law enforcement. We'll continue to monitor the situation & provide federal support, as we pray for comfort & healing for all impacted."

Fox News' Adam Housley and Shira Bush and the Associated Press contributed to this report.